Label switched packet transfer device

ABSTRACT

A device for connecting base station(s) to a cellular label switched network in a cellular network. The cellular network includes: base station(s), the connecting device(s); cellular label switched network(s); and service area(s). The base station(s) communicates with mobile terminals using wireless technology. The wireless technology uses a protocol layer architecture that includes at least one of the following: a wireless physical layer; a wireless medium access control protocol layer; a radio link control layer; and a network layer. The connecting device(s) include: a first interface to connect to the base station(s); a second interface to connect to cellular label switched network(s); and a label forwarding layer that: forwards packets between base station(s) and cellular label switched network(s); attaches label(s) to packets and removes label(s) from packets. A service area divided into a multitude of cells through which mobile terminals can move through and communicate with base station(s).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/167,295, filed Jun. 23, 2011, which is a continuation of U.S. patentapplication Ser. No. 12/609,556, filed Oct. 30, 2009, now U.S. Pat. No.8,213,424, which is a continuation of U.S. patent application Ser. No.11/419,286, filed May 19, 2006, now U.S. Pat. No. 7,616,599, which is acontinuation of U.S. patent application Ser. No. 09/956,466, filed Sep.20, 2001, now U.S. Pat. No. 7,061,896, which claims the benefit ofprovisional patent application No. 60/234,167, filed on Sep. 20, 2000,which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention generally relates to the field of network packettransfer. More specifically, the present invention relates to packettransfer mechanisms in wireless cellular networks.

The increasing dependence on the Internet and the wide-spread use ofwireless terminals have given rise to considerable interest in thedevelopment of a wireless Internet. In particular, such wirelessnetworks are expected to provide efficient packet transfer and supportmultimedia applications. Of importance in the wireless segment is theflexibility in allocation of bandwidth and efficient use of radioresources. In the core networks, multi-protocol label switching isemerging as a technology to facilitate traffic engineering andinternetworking. Label switched transfer is an extension to packetforwarding whereby short fixed length labels are attached to packets atan entry node to provide a path to an exit node. What is needed is anarchitecture, using label switching, to support wireless mobileterminals.

ATM has been used to a certain extent as a switching technology forbackbone networks to support integrated services with QoS control.Considerable research has been carried out to extend ATM services tomobile terminals mostly with the assumption that ATM connectionsterminate at the wireless users. For example, Wireless-ATM (WATM), mayextend the ATM signaling and control framework to support mobility. Onthe other hand, with the widespread use of Internet protocols, manyschemes have been proposed to support mobility for IP wireless terminalswithin a connection-oriented framework of ATM networks.

Connection-oriented transfer mode requires segments of the connection tobe released and reestablished, thus leading to significant complexitywhen the end points move. Connectionless mode, on the other hand, maysimplify adaptation to changes in particular when mobility and hand-offare present. What is also needed is an architecture that takes advantageof both transfer modes without the complexity of Wireless-ATM.

The cellular industry needs an architectures that involve minimalrequirements at the mobile terminal, and allows the mobile terminals tobe interconnected to the backbone network. This architecture shouldinclude mechanisms for location and handoff management as well as labelmerging capability and fast rerouting schemes to support multilinktechniques and mobility.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate an embodiment of the present inventionand, together with the description, serves to explain the principles ofthe invention.

FIG. 1 is a diagram of an aspect of the present invention showing ahierarchical structure for wireless label switched networks.

FIG. 2 is a diagram of an aspect of the present invention showing awireless label switching protocol layer architecture.

FIG. 3 is a diagram of an aspect of the present invention showingreachability information distribution for location management androuting.

FIG. 4 is a block diagram of an aspect of the present invention showingrerouting of label switched paths during handoff from a first basestation to a second base station.

FIG. 5 is a block diagram of an aspect of the present invention showinga label switched path tree in a cellular label switched network.

FIG. 6 is a block diagram of an aspect of the present invention showingmultilink and label merging for users in diversity areas.

FIG. 7 is a graph showing overload probability versus the number ofadmitted mobile terminals for different percentage of diversity areas.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method and apparatus to support ahierarchical architecture which integrates wireless mobile terminalsinto networks such as the Internet. This architecture provides forefficient packet transfers over mobile wireless networks by efficientlyallocating wireless resources. Label Switched packet forwardingfacilitates traffic engineering and internetworking by attaching shortfixed length labels to communications packets at an entry node to awireless network to provide an efficient path to an exit node of thesame wireless network. Forwarding mechanisms and limited broadcasting ofreachability information may be used in managing and routingcommunications packets through wireless mobile networks. The presentinvention also supports multiple radio links between a mobile terminaland a multiplicity of base stations. Multi-link techniques are used toaffect an efficient packet transfer and admission policy.

A path may be established between any two nodes of a network to carrydatagram traffic. The connection between the two nodes may be known as alabel switched path and the two nodes may be label switching routers. Asdisclosed, multi-protocol label switching may provide certain advantagesof connection-oriented network while retaining efficiency of thedatagram network.

An embodiment of the present invention showing a hierarchical structurefor wireless label switched network is depicted in FIG. 1. LabelSwitching networks 130 and 140 are connected to a backbone network 110and a fixed network 120. The network may include a multitude of basestations such as base stations 151, 152, 153, 154, 155, 156, 157, 158,and 159, connected to label switching nodes (LSN) such as 131, 136, 142and 143, along with components of a standard multi-protocol labelswitching network, such as label switching routers. The label switchingnodes (131, 136, 142 and 143) may provide services to the base stations(151, 152, 153, 154, 155, 156, 157, 158, and 159) and may also supportfast handoff and location management mechanisms. The hierarchicalarchitecture preferably extends label-switched paths to the basestations (151, 152, 153, 154, 155, 156, 157, 158, and 159), which inturn may support wireless users. The wireless users typically will use amobile terminal 170 to communicate through the network. The architecturedisclosed here may be independent of the underlying radio technology.The base station terminating the label-switched paths preferably havefunctions for forwarding packets between wireless terminals and labelswitching node interfaces.

Service areas may be divided into microcells (161, 162, 163, 164, 165,166, 167, 168, and 169) with base stations (151, 152, 153, 154, 155,156, 157, 158, and 159) connected to label switching nodes (131, 136,142 and 143), which preferably provide control and concentrate basestation traffic. A routing area may be defined to support the mobilityof the users 170 and may store location information of the mobileterminals, such as 170, in the network. A routing area may consist of aset of cells with base stations connected to the same label-switchingnode. As illustrated, a first routing area consists of cells 161, 162,and 163 connected to node 131. A second routing area consists of cells164, 165, and 166 connected to node 136. Location information may beupdated when the mobile terminal 170 enters a new routing area. Sincethe geographical coverage of a routing area may be large compared to thesize of the radio microcells (160, 161, 162, 163, 164, 165, 166, 167,168, and 169), the rate of routing area handoff may be acceptably low.The present invention considers fast signaling among label switchingrouters and label switching nodes. That means, for example, that routingtables may be updated in a time much shorter than the frame duration inthe radio link.

A connection may be made between a pair of the label switching nodes,where each of the pair of label switching nodes resides in separatecellular label switched networks. For example, node 135 which resides incellular label switched network 130, and node 141 which resides incellular label switched network 140, may be connected by connection 180.

FIG. 2 is a diagram of an aspect of the present invention showing awireless label switching protocol layer architecture which includes awireless terminal label switching protocol layer architecture 210, abase station label switching protocol layer architecture 220, and alabel switching node label switching protocol layer architecture 230.The wireless terminal label switching protocol layer architecture 210includes a network layer 211, a radio link layer 212, a wireless mediumaccess control (MAC) layer 213, and a wireless physical layer 214. Thebase station label switching protocol layer architecture 220 includes anetwork layer 221, a radio link layer 222, a wireless medium accesscontrol layer 223, a wireless physical layer 224, a multi-protocol labelswitching forwarding layer 225, and a physical layer 226. The labelswitching node label switching protocol layer architecture 230 includesa network layer 231, and a multi-protocol label switching forwardinglayer 235, and physical layers 236 and 237.

There are two main issues in the physical medium when wire line networksare extended to wireless terminals. Wireless media usually have atime-varying link quality and provide a point-to-multipoint broadcastenvironment, which may necessitate the development of a different mediaaccess scheme. The protocol layer architecture shown in FIG. 2 addressesthese issues to enable the development of wireless label switchednetworks. The wireless medium access control layers 213 and 223 supporttransmission of different traffic classes by wireless terminals overradio links. The radio link control segments 212 and 222 may transformmobile packets into radio link frames and may use error mitigationmechanisms to enhance poor radio link quality. Radio link frames may beassigned to mobile terminals by radio link identifier. Base stations mayreassemble the radio frames to data packets, attach the label andforward the labeled packet.

Location management preferably allows the network to keep track ofmobile terminal user's current location and thus simplifies theforwarding of the incoming calls to the mobile terminal. Locationmanagement may also bring user's profile near to its location and allowthe network to provide the user with subscribed services. No separatemobile terminal locating procedure prior to connection setup may beneeded.

The present invention extends the current interior gateway protocols tothe disclosed architecture supporting mobile terminal users. Link staterouting protocols, such as IS-IS [8] or OSPF [9] in a multi-protocollabel switching domain, may broadcast the network state to compute apath through the network topology. Once a path has been computed,signaling protocols may be used to establish a label switched path, andtraffic that satisfies the forwarding equivalence class relationship maybe sent down the label switched path. These paths may be computed basedon topology state information database existing in label switchingrouters throughout the network and shared among neighbors.

FIG. 3 is a diagram of an aspect of the present invention showingreachability information distribution for location management androuting. As illustrated, backbone network 300 is connected to cellularlabel switching networks 310 and 350. Service area 390 is connected tocellular label switching networks 310 via node 333. Routing areas mayeffectively limit the registration traffic and routing updates arisingdue to cell crossovers by mobile terminals. To locate a mobile terminal,the network may find the routing area where the mobile terminal islocated instead of tracing the base station to which the mobile terminalis connected. This may be done by updating the changes in the mobileterminal's routing area.

Some nodes in the cellular switching networks 310 and 350, may beorganized to form groups of nodes. The nodes may include label switchingrouters and label switching nodes. For example, cellular label switchingnetwork 310 as shown is organized into groups 320, 330 and 340.Likewise, cellular label switching network 350 as shown is organizedinto groups 360, 370 and 380. To further reduce the routing updates, onenode among the group may be represented in the network to share topologyinformation of its group. In cellular label switching network 310, node322 is representing group 320, node 332 is representing group 330, andnode 342 is representing group 340. In cellular label switching network350, node 362 is representing group 360, node 372 is representing group370, and node 382 is representing group 380. These representativesconstitute the next higher layer and they may be further grouped to forma multi-layer architecture covering the whole cellular label switchednetwork. Note that as shown, nodes 322 and 362 may be label edgerouters. There may be a trade-off between the propagation of theinformation to the higher layers and the amount of routing updatesneeded for the location management. The highest level in which thelocation information is distributed may define the reachability region.The topological state updates may be propagated within the reachabilityregion to indicate where the mobile terminals are located and to enablethe label switching routers to have exact location information about themobile terminals.

In case of an incoming call for a mobile terminal, there are twopossibilities; either the caller is in the same reachability region asthe mobile terminal, or the caller is outside. In the former case, thenetwork may locate the mobile terminal using the location updates in thelabel switching routers and label switching nodes. Therefore, incomingpackets may be directly delivered to a mobile terminal using a shortestpath algorithm. In the latter case, the path set up may be directed to amobile terminals home. Here, there are two further possibilities,whether the called mobile terminal is within its home reachabilityregion or the called mobile terminal is outside. In the former case, thecall may be directly delivered to a mobile terminal since all the labelswitching routers have its exact location information. In the lattercase, the path setup may be directed towards the home of the calledmobile terminal and it may then be forwarded by the home to the mobileterminal's current location.

Groups may maintain identical topological databases (reachabilityupdates). The area's topology may be invisible to the entities outsidethe area. Area border nodes may be responsible for inter-area routing.This hierarchy may limit traffic due to the distribution of thereachability information among nodes in a particular area and in thecomplete autonomous system.

In fixed networks, after a connection has been established, theconnection path may not change unless there is a link or a node failure.This situation is no longer valid in the mobile networks where the endusers are continuously moving. Due to this behavior, the path to themobile terminal may need to be rerouted based on its current location. Ahandoff is the process of rerouting a path as a mobile terminal moves.The handoff process dealing with the connection rerouting may consist ofthree steps. First, finding a path and establishing a label switchedpath to the new base station; second, enabling the mobile terminal toreceive and transmit via both old and new base stations when it is inthe diversity area (area covered by both base stations); and third,shifting the data path at the crossover switch to the new label switchedpath, thus extending the traffic flow to the mobile terminals node whenit has completely moved under the new base station's coverage.

The present invention may handoff execution in a cellular label switchednetwork 420 using at least the following two rerouting schemes asillustrated in FIG. 4, which is a block diagram of an aspect of thepresent invention showing rerouting of label switched paths duringhandoff from a first base station 442 to a second base station 452. Afirst rerouting scheme involves dynamic rerouting. A second reroutingscheme involves rerouting by using pre-established paths.

Dynamic routing is based on the modification of an old path to find anew (and preferably optimal) path to the new location of the mobileterminal user. This scheme involves searching for the last common nodeof the old and new paths, and then switching the traffic at the commonnode to the new path. This common node is termed as the crossover switchand this mechanism may be called crossover switch discovery.

As illustrated, the mobile terminal 470, in communication with a host400, moves from a first region 440 covered by the first base station 442to a second region 450 covered by a second base station 452. Toeffectuate a handoff from first base station 442 to second base station452, a first path 480 is switched to second path 490. The old labelswitched path tunnel 480 (routed from node 431 to node 432 to node 434to first base station 442) may be rerouted from the crossover switch 432to the second base station 452. The first subpath (node 432 to node 434to second base station 442) may be torn down after the data stream issuccessfully mapped to the new subpath (node 432 to node 433 to secondbase station 452). It may be desirable that the traffic is not affectedduring rerouting, and that there is no adverse impact on the network.The present invention may adapt the policy of make-before-break as itexists in the fixed multi-protocol label switching network (e.g., usingRSVP as the signaling protocol). The smooth rerouting of the traffic mayrequire establishment of a new label switched path tunnel andtransferring the traffic from the old label switched path 480 to the newlabel switched path 490 before tearing down the old label switched path480. The two label switched paths may share the resources along thepaths in common. Over the radio links additional messages between thebase stations and mobile terminal may be exchanged to complete handoffprocess.

Rerouting by using pre-established paths involves setting of apre-established tree between the base stations, 442 and 452, located inthe region of influence of the mobile terminal 440 and 450, and somecommon node 432 (where these paths converge) prior to handoff. When theuser moves from the first base station 442 to the second base station452, the network selects different branches of the tree forcommunication.

FIG. 5 is a block diagram illustrating an aspect of the presentinvention showing how a label switched path tree may be established in acellular label switched network. Label switched paths may be exploitedto accommodate high rate of handoff among the base stations in a givengeographical area (region of influence of the mobile terminal). The rootof the tree is a node 502 may be a label switching router and isconnected to node 501. The leaves of the tree may be base stations 511,512, 513, and 514. Nodes 503 and 504 are branch nodes. This tree issimilar to point to multipoint connection tree in which only one path isin use at a time. When a mobile terminal is admitted to the connectiontree, a call setup procedure may consist of two phases. The initialphase may include establishment of paths from the root of the tree (node502) to the other end of the connection (node 511, 512, 513, or 514) andmay be maintained as long as the mobile terminal remains within the sametree. The second phase may include setting of the paths within theconnection tree (root and the base station). Two label switched pathidentifiers may be allotted to the label switched path between the basestation and the root of the tree (one in each direction). Also, withinthe multi-protocol label switching framework, and with certainextensions to the existing signaling protocol bi-directional tunnels maybe established as a single process, between the base stations (node 511,512, 513, or 514) and the root (node 502) of the tree.

When a mobile terminal who is already admitted to a connection treewishes to handoff to another base station in the same geographical area(covered by the same tree), it may simply begin transmitting radiopackets to the new base station and the traffic may be further forwardedto the destination through the fixed network. After the handoff, theroot of the tree may receive the packets from the same mobile terminalwith a new label and a different label switched path identifier. Theroot node may update its routing tables so that future packets may bedelivered to the new base station of the given mobile terminal. This maymark the completion of the handoff process. If the mobile terminalreaches the edge of the geographical area covered by the same tree, itmay request a tree handoff. Since the area covered by the tree may belarge, tree handoffs may be less frequent.

Experience gained in the design and planning of cellular systemsindicates that there may be a considerable amount of diversity areasamong cell segments. In a diversity area, a mobile terminal may be in anoverlapping area wherein the mobile terminal may receive and transmitradio packets from and to two or more base stations. Transmission andhandoff procedures in diversity areas may be important because they canaffect the communication quality during handoff and change the overallsystem capacity. The present invention expands upon multilinktechniques, in which a mobile terminal in the diversity area mayestablish packet links to a plurality of base stations capable ofcommunicating to it. The network may balance the traffic between thelinks based on the link quality and system available capacity.

FIG. 6 is a block diagram of an aspect of the present invention showingmultilink and label merging for users in diversity areas. The presentinvention may support multilink techniques that allow multiple parallellabel switched path tunnels between nodes and the traffic between thenodes to be mapped to the label switched path tunnels according to alocal policy. In addition, the present invention provides for labelmerging. Label merging occurs when a node such as a label switchingrouter receives multiple packets through different incoming interfacesor with different labels forwarding the multiple packets over the sameoutgoing interface with the same label.

Label merging occurs when a node 612 such as a label switching routerreceives a first packet 621 and a second packet 622. FIG. 6 shows howthis capability may be exploited in an uplink scenario. Mobile terminal643 may transmit a first packet 621 and a second packet 622 to both afirst base station 631 and a second base station 632. The first basestation 631 may forward packet 621 to node 612 with a first label.Likewise, the second base station 632 may forward packet 622 to the samenode 612 with a second label. Node 612 may act as a merging point, andforward both the first packet 621 and the second packet 622 with thesame label as new first packet 623 and new second packet 624 to upstreamnode 610 (and then to a destination). In a downlink scenario the nodemay establish two separate label switched paths (one with the first basestation 631 and another with the second base station 632) to a samedestination, such as mobile terminal 643. The load may be balanced onthese label switched paths dynamically based on the local policies.

The Handoff process in a pre-established path tree may require admissioncontrol of mobile terminal connections to the tree since, once a mobileterminal is admitted to the connection tree, it may freely hand-off toany base station within the connection tree. This may lead tooverloading or congestion at a given base station if the number ofmobile terminals seeking access to the network through the given basestation exceeds the capacity of the base station. The purpose ofadmission control is to limit the number of mobile terminals attached tothe tree at any given time to prevent the overloading of the basestation and maintaining the desired QoS.

Here, consider base station overload probability as a QoS parameter,which is controlled by connection tree admission control. Consider aconnection tree similar to the one shown in FIG. 5. Assume that thereare N users admitted to the connection tree and each of them is free toselect any of the base stations in the connection tree, then theprobability that there are i connections established with a particularbase station, Pi, may be given by binomial distribution:

$\begin{matrix}{P_{i} = {{\begin{pmatrix}N \\i\end{pmatrix}\left( \frac{1}{B} \right)^{i}\left( \frac{B - 1}{B} \right)^{N - i}} = {\begin{pmatrix}N \\i\end{pmatrix}\left( \frac{1}{B - 1} \right)^{i}\left( \frac{B - 1}{B} \right)^{N}}}} & (1)\end{matrix}$

B is the number of base stations in the connection tree and 1/B is theprobability that a mobile terminal is communicating with a particularbase station. If a base station can support up to m connections, theprobability of overloading may be given by

$\begin{matrix}{P_{o} = {{\sum\limits_{i = {m + 1}}^{N}P_{i}} = {\left( \frac{B - 1}{\; B} \right)^{N}{\sum\limits_{i = {m + 1}}{\begin{pmatrix}N \\i\end{pmatrix}\left( \frac{1}{B - 1} \right)^{i}}}}}} & (2)\end{matrix}$

The overloading probability may be improved by the use of a multilinktechnique. Users in the diversity areas may communicate with both basestations. Considering a simple algorithm in which users in the diversityareas first request for a connection from the base station with thelower load. In other word, if a base station is overloaded by i>mconnection requests, it transfers i−m calls to the neighboring basestations. This is possible if at least i−m mobile terminals are in thediversity areas and neighboring base stations have enough capacity tosupport them. Let us consider two neighboring cells (as shown in FIG.6), in which a mobile terminal is in a diversity area with probabilityPd. Then the overlapping probability may be re-evaluated as follows:

$\begin{matrix}{P_{o} = {{\sum\limits_{i = {m + 1}}^{2m}{P_{i} \times \left( {1 - {P_{t}\left( {i - m} \right)}} \right)}} + {\sum\limits_{i = {{2m} + 1}}^{N}P_{i}}}} & (3)\end{matrix}$where Pt(i−m) is the probability that i−m calls are successfullytransferred to the other base station and it may be calculated asfollows:

$\begin{matrix}{{{{Pt}\left( {i - m} \right)} = {{P\left( {{{number}\mspace{14mu}{of}\mspace{14mu}{mobile}\mspace{14mu}{terminals}\mspace{14mu}{in}\mspace{14mu}{diversity}} > {i - {m/i}} > m} \right)} \times {P\left( {i < {{2m} - i}} \right)}}}{{and}\mspace{14mu}{then}}{{P_{t}\left( {i - m} \right)} = {\left\{ {\sum\limits_{k = {i - m}}^{i}{\begin{pmatrix}i \\k\end{pmatrix}{P_{d}^{i}\left( {i - P_{d}} \right)}^{N - i}}} \right\} \times {\sum\limits_{i = 0}^{{2m} - i}P_{i}}}}} & (4)\end{matrix}$

The analysis may be more complex when more than two cells areconsidered. A simulation study may be performed to measure the effect ofload balancing capability on overload probability. Considering aconnection tree containing B=7 base stations, each capable of supportingm=50 users, FIG. 7 shows the effect of the diversity areas on theperformance of the call admission policy. Overload probability maysignificantly decrease by using multilink technique.

A hierarchical architecture has been disclosed which may provideservices to wireless mobile terminals using label switched networks.Location management and routing issues are addressed by using forwardingmechanisms and limited broadcasting of reachability information. Thepresent application discloses how multi-protocol label switching labelmerging and rerouting capabilities may be used to support multilinktechnique and mobility. Also disclosed are multilink techniques that mayimprove the performance of the admission policy by an order of magnitudedepending on the diversity areas.

A cellular network as per the present invention may comprise a servicearea divided into a multitude of cells through which one or more mobileterminals may move through. Base stations capable of communicating withthe mobile terminals may be deployed in each of the multitude of cellsfor forwarding packets between the base stations and the mobileterminals. The cellular label switched network may also include aplurality of nodes topologically connected. At least one of the nodes ispreferably a label switching node. A connection between base stationsand at least one label switching node may allow for forwarding packetsbetween the base stations and the label switching nodes.

A label switched path for directing packets between a pair of locationsmay be determined. Each location in the pair is preferably a node or abase station. A label may then be attached to the packets. The packetsmay include the label switched path and control information. Labels maybe removed from the labeled packet by a node and interpret by the nodesto determine how to forward the packet along the label switched path.

At least one of the label switching nodes is preferably a label edgenode. At least another of the of the label switching nodes is preferablya device, a switch or a router. The nodes in a system may include butare not to be limited to devices, switches and routers.

In a cellular network as per the present invention, any node such aslabel edge routers may be an ingress node, an egress node, or aningress/egress node.

The label switched nodes preferably provide base station controlinformation to the base stations, may concentrate traffic to the basestations, may provide support for fast handoff of the mobile terminalsto the base stations, and may further provide location managementinformation to the base stations.

Connections may also be made between a pair of the label switchingnodes, where each of the pair of label switching nodes resides inseparate cellular label switched networks. This allows for multiplenetworks to be coupled, thus forming a larger cellular network.

Base stations preferably use wireless technology to communicate with themobile terminals. The wireless technology may utilize radio technology,optical technology, or other type of wireless technology where data maybe communicated between two points without the assistance of wire.

The network may use optical technology at other locations too, includingany of the nodes or connections. The optical technology may include freespace optical switching technology or guided optical switchingtechnology.

The wireless technology may use a protocol layer architecture which mayinclude but is not limited to a wireless physical layer, a wirelessmedium access control protocol layer, a radio link control layer, or anetwork layer. These elements may be found on both the base stations andwireless terminals. The radio link controls may segment mobile packetsinto radio link frames which may be identified by radio linkidentifiers. Various techniques known to those skilled in the art may beemployed for error mitigation to enhance poor radio link quality. Thebase station may reassemble radio frames received from mobile terminalsinto packets. One way to accomplish this includes attaching the label tothe packets and then forwarding the labeled packets to the labelswitching node. Likewise, the base station may also process packetstraveling in the opposite direction. When the base station receiveslabeled packets from a label switching node, the base station maysegment the labeled packets into radio frames, remove the labels fromthe labeled packets, and then forwards the radio frames to the mobileterminal.

The label switched path may be determined by information derived frombroadcasting a network state through the network topology using arouting protocol, and then establishing the label switched path using asignaling protocol. The routing protocol may be a link state routingprotocol, a vector space routing protocol, or any other known routingprotocol. The label switched path may also be determined by a topologydatabase. In some embodiments of the present invention, the topologydatabase may exist in a multitude of the nodes. It may even bepreferable for the topology database to be shared among its neighbornodes.

The cellular network may further include a plurality of routing areas,wherein each of the routing areas include a set of cells whose basestations are connected to the same label switched node. These routingareas may further include mobile terminal location information. Themobile terminal location information is preferably updated whenever themobile terminal enter a new routing area. The mobile may be located bydetermining which of the plurality of routing areas the mobile terminalis located.

The cellular labeled switched network may be a multi-layer cellularlabeled switched network. This multi-layer cellular labeled switchednetwork may be divided into a plurality of smaller groups, where each ofthe smaller groups consisting of a multiplicity of label switched nodeshave topological databases. Some or all of these topological databasesmay be maintained to be identical, and may further include reachabilityupdates. These topologies of the smaller groups may also be invisible toentities outside the smaller group. At least one of the nodes in atleast one of the smaller groups may be an area border node responsiblefor inter-group routing. Similarly, when there are a multitude ofcellular labeled switched networks, at least one of the nodes in each ofthe multitude of cellular labeled switched networks may be an areaborder node responsible for inter-cellular labeled switched networkrouting.

The present invention includes a mobile terminal hand-off mechanismincluding the steps of finding a new data path from the mobile to a newbase station, using the new data path to establish a new label switchedpath to the new base station, enabling the mobile to receive andtransmit to both the old base station and the new base station when themobile is in a diversity area, shifting the data path at a crossovernode to the new label switched path; and extending traffic flow to newbase station when the mobile has completely moved under the new basestation's coverage.

Label merging may be accomplished by receiving two or more packets withdifferent labels, and forwarding the two or more packets over a singleoutgoing interface with a singular label. At least two of the receivedpackets may be received through different incoming interfaces of atleast one of the label switching nodes. Further, the packets may bereceived from at least one of the base stations.

A label switched path tunnel may be used between a pair of the nodesalong a label switched path. Traffic between the pair of nodes may bemapped through the label switched path tunnel according to a localpolicy. The local policy may specify how may packets may travel throughthe tunnel at one time, or may specify what kind of traffic may travelthrough the tunnel. Any type of traffic decision may be made by thepolicy. It may be preferable if at least one of the nodes is capable ofestablishing at least two separate label switched path tunnels to theother node.

Traffic loading may be balanced on label switched paths dynamicallybased on local policies. A label switched path may be rerouted byestablishing a new label switched path tunnel, transferring traffic fromthe label switched path to the new label switched path, and thenremoving the label switched path. Resources may be shared between thelabel switched path and the new label switched path along their commonpaths. The label switched path may also be rerouted usingpre-established paths. This may accomplished by: setting apre-established tree between the base stations located in the region ofinfluence of the mobile and a common node prior to handoff; andselecting a different tree branch for communication when the mobileterminal moves from one of the base station to the another one of thebase stations.

Additional messages between the base stations and the mobile may beexchanged to complete handoff and the cell selection process. The cellselection process may include cell reselection. In addition, whenever amobile terminal reaches the edge of a geographical area covered by anactive tree, the mobile terminal may requests a tree handoff.

In an embodiment of the present invention, the mobile terminal mayreceive and transmit radio packets to and from a multitude of basestations. When a mobile terminal is in a diversity area, the mobileterminal may establish packet links to a multitude of base stationscapable of communicating to the mobile terminal.

The network may consider factors when balancing traffic. Examples offactors that may be considered include link quality and systemavailability.

During a hand-off in a pre-established path tree, the handoff mechanismutilize admission control of mobile connections to the tree. An overloadprobability value may also be used as a factor in the admission control.Determination of the overload probability value may include the numberof users, the number of base stations, and the number of connectionseach base station can support.

The foregoing descriptions of the preferred embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The illustrated embodiments were chosen and described in orderto best explain the principles of the invention and its practicalapplication to thereby enable others skilled in the art to best utilizethe invention in various embodiments and with various modifications asare suited to the particular use contemplated.

What is claimed is:
 1. A method for transmitting packets in a network,the method comprising: receiving, at a network node in a cell site inthe network, a first packet from a base station associated with the cellsite; appending, by the network node, information to a header of thefirst packet, the information identifying a path through a backbonenetwork, wherein appending information to the header of the first packetcomprises attaching a first label to the first packet, the first labelidentifying a first label switched path through the backbone network;and forwarding the first packet with the appended information to aswitching node in the backbone network.
 2. The method of claim 1,further comprising: examining, by the switching node, the first label;and based on examining the first label, determining, by the switchingnode, a transmission path of the first packet along the first labelswitched path.
 3. The method of claim 1, wherein identifying the firstlabel switched path includes identifying a Multiprotocol Label Switching(MPLS)-based path.
 4. The method of claim 1, further comprising:receiving a second packet from the switching node, the second packetincluding information appended to a header of the second packet thatidentifies a second path through the backbone network; removing theinformation appended to the header of the second packet; and uponremoving the information, transmitting the second packet to the basestation.
 5. The method of claim 4, wherein the information appended tothe header of the second packet includes a second label attached to thesecond packet, and wherein the second path includes a second labelswitched path through the backbone network.
 6. The method of claim 4,wherein at least one of the first packet or the second packet includesan IP (Internet Protocol) packet.
 7. The method of claim 6, wherein theIP packet includes a header section, the header section including atleast one of a source address or a destination address.
 8. The method ofclaim 4, wherein the network node is coupled to a radio component thatis located at the cell site and configured to communicate wirelesslywith a mobile wireless terminal over a radio link, the methodcomprising: receiving, using the radio component, one or more radio linkframes from the mobile wireless terminal; and assembling the one or moreradio link frames into the first packet.
 9. The method of claim 8,further comprising: receiving the second packet from the switching nodein the backbone network; segmenting the second packet into one or moreradio link frames; and transmitting, using the radio component, the oneor more radio link frames associated with the second packet to themobile wireless terminal.
 10. The method of claim 8, wherein the networknode includes a switching component, the method further comprising:assembling, using the switching component, the one or more radio linkframes into the first packet; appending, using the switching component,the information to the header of the first packet; removing, using theswitching component, the information appended to the header of thesecond packet; and segmenting, using the switching component, the secondpacket into the one or more radio link frames.
 11. A network node thatis configured to transmit packets in a network, wherein the network nodeis configured to: receive a first packet from a base station associatedwith a cell site in the network; append information to a header of thefirst packet, the information identifying a path through a backbonenetwork, wherein appending information to the header of the first packetcomprises attaching a first label to the first packet, the first labelidentifying a first label switched path through the backbone network;and forward the first packet with the appended information to aswitching node in the backbone network, wherein the network node isplaced in the cell site.
 12. The network node of claim 11, whereinidentifying the first label switched path includes identifying aMultiprotocol Label Switching (MPLS)-based path.
 13. The network node ofclaim 11, wherein the network node is coupled to a radio component thatis located at the cell site and configured to communicate wirelesslywith a mobile wireless terminal over a radio link, and wherein thenetwork node is configured to: receive, using the radio component, oneor more radio link frames from the mobile wireless terminal; andassemble the one or more radio link frames into the first packet. 14.The network node of claim 13, wherein the network node includes aswitching component, the network node further configured to: assemble,using the switching component, the one or more radio link frames intothe first packet; and append, using the switching component, theinformation to the header of the first packet.
 15. The network node ofclaim 14, wherein the switching component is co-located with the radiocomponent.
 16. The network node of claim 11, wherein the network node islocated at an interface region between the cell site and the backbonenetwork.
 17. The network node of claim 11, wherein the network node isassociated with a cell site gateway.
 18. The network node of claim 11,wherein the network node is included in the base station.
 19. A systemcomprising: a base station associated with a cell site in a network; aswitching node in a backbone network associated with the network; and anetwork node placed in the cell site and configured to forward packetsbetween the base station and the switching node, wherein the networknode is configured to: receive a first packet from the base station;append information to a header of the first packet, the informationidentifying a path through the backbone network, wherein appendinginformation to the header of the first packet comprises attaching afirst label to the first packet, the first label identifying a firstlabel switched path through the backbone network; and forward the firstpacket with the appended information to the switching node.